Objectives: Licensure of acellular pertussis vaccines for infant use was dependent upon the evaluation of recently completed efficacy trials. Comprehensive understanding of diagnostic procedures used in these trials to diagnose Bordetella pertussis infection was necessary for reviewers to make informed decisions on licensure and recommendations for use. With increasing use of acellular pertussis vaccines in the US, adequate surveillance of the immunization program and evaluation of outbreaks will require improved and innovative diagnostic approaches for all age groups. These techniques must improve on the sensitivity and specificity of currently available methods. To increase knowledge of pertussis diagnosis and epidemiology, the Laboratory has initiated projects: a) To develop and improve laboratory procedures to diagnose infection with B. pertussis, b) To determine which diagnostic procedures have the highest sensitivity and specificity for pertussis diagnosis at the different stages of illness and ages of patients c) To apply these techniques to understand epidemiology of pertussis. FY99 Activities: Provided ongoing technical advice and support for CDC contract entitled: "Measurement of antibodies to three antigens of Bordetella pertussis." The goal of the study is to develop pertussis serodiagnostic assays that can be transferred to state and regional clinical laboratories.